I export a sketchup file in .atl, my textures are pixelized, and when i put the lamp to diffuse the light, i have to put it up to 60 000 lumens to bright even a little bit. I also see my plan just like a surface in 2D view, and not the architectural plan as it shows normally!!!
The pixelisation depends on the texture size and definition, I cannot tell you without seing the image.
For the lighting and the lumen value, you should not need to use an unrealistic value, what you need to do is set the ISO/Shutter to a realistic value.
I would suggest to contact the support and send them your file, they should be able to help you choose the correct setting.